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Various analyses of goat milk in 10 different countries 8, 18 indicates a wide variation in total solids, fat, protein, lactose and ash content. In Table 2 the highest, lowest and average findings can be seen. In the experience of the authors, apart from a regional factor, a wide seasonal variation in the composition of goat milk can occur. The canned product available in South Africa is, therefore, standardized and an analysis on this product is also included in Table 2. No analysis on the American product is available but it is assumed that it will be more or less the same.
Variation in Composition of Goat Milk
The Protein of Goat Milk
Webb and Johnson19 reported that in general the distribution of the different components of goat milk protein are similar to that of cow milk and that the casein fraction is nearly the same elementary composition as bovine casein. Hofman,20 however, showed by electrophoresis that the distribution of the various components in the casein of cow and goat milks are quite different. The casein in cow milk consists of 55% alpha casein, 30% beta casein and 15% k casein, while that of goat milk contains 19% alpha 1, 21% alpha 2 and 60% beta casein.21
The casein of goat milk has more glycine, less arginine and less sulphur-containing amino acids (particularly methionine) than cow milk.22
The most recent work which contributed immensely to our knowledge of goat milk was done in France by Ribadeau Dumas et al23 on the molecular structure of the polymorphs of the caseins.
It was for the first time possible to demonstrate the molecular structure of bovine milk casein. The molecular structure of goat milk was done immediately afterward and it was proved beyond doubt that goat niilk casein differed widely in basic chemical structure from that of cow milk. The author concluded it now was possible to say that not only the lactalbumin but all the various fractions of protein in goat milk differ from that in cow niilk. This, then, is the likely reason why an infant intolerant to a product from cow milk does so well on goat milk.
The Curd Tension of Goat Milk
The curd tension of goat milk is much lower than that of cow milk. The average values with pepsin - HCl were 36, 52 and 78 for goats, Holstein-Friesian and Jersey milk respectively. This may account for the said better digestibility of goat milk as compared to cow milk.
The Nutritive Value of Goat Milk in Feedng Experiments with Infants
On an equal energy intake, goat milk and cow milk are comparable in promoting growth of human infants.24, 32 Daniel and Stearns25 found a somewhat lower nitrogen retention in five infants receiving goat milk as compared with cow milk. They found no significant difference in the retention of calcium and phosphorous by these infants.
The Immunological Properties of Goat Milk Protein
Most text books on allergy and pediatrics state that goat milk may be used as a substitute for cow milk hypersensitivity. The reason given being the whey proteins of goat milk and. cow milk are thought to be imnunologically distinct. This concept dates back to the carly work of Versell.26
Crawford and Grogan27 with precipitation-in-gel experiments cast doubt the species specificity of the whey proteins of cow and goat milk, and also demonstrated almost identical casein precipitation patterns of both inilks. These authors, therefore, assumed they have demonstrated by means of this diffusion-in-gel method an antigenic relationship between goat and cow milk which makes goat milk unsuitable for a patient with cow milk allergy. Saperstein28 also came to a similar conclusion by means of precipitation and anaphylactic tests using rabbit immune sera against Alpha lactalbumin and Beta lactoglobulin. Later work, however, done by Hanson and Anderson29 questions the value and accuracy of the above methods. A similar relationship between the corresponding proteins in human and bovine milk was demonstrated using the above mcthods, although in practice it was found that infants with a cow milk allergy could tolerate breast milk.
Hanson and Anderson29 quote Augustin who criticized the use of sera from hyperimmunized animals in diffusionin-gel methods to study adergens. The antigenic properties demonstrated in this way may have no bearing upon their allergenicity. The findings of Hanson and Anderson “seem to indicate that antigenic relationships, as revealed by hyperimmune sera from animals in diffusion-in-gel methods, may not be assumed to demonstrate any allergen!city of substances antigenically related to known allergens; for example, for goat milk proteins in a patient with cow milk allergy.”
The Fat of Goat Milk
Goat milk creams much less rapidly and completely by gravity than cow milk. This is due to the much srnaller size of the fat globules30 in goat milk and also due to a lack of fat globule clustering agent31 in goat milk. Goat milk differs from cow milk in that it contains more of the essential fatty acids (linoleic and arachidonic) and it has a greater percentage of medium and shortchain saturated fatty acids. These differences suggest that the fat of goat milk may be more readily digested than that of cow milk.32 Data regarding the fatty acid composition of goat milk fat is compared with those of human and cow milk fat is given in Table 3.
Animal Milk& & Human Milk
|Linolenic Acid||0.4||- -||- -|
It will be noted that goat milk fat contains more Caproic, Caprylic, Capric and Lauric acid than cow milk fat. The contents of Palmitic and Stearic acids are almost of the samc order and of Oleic acid somewhat less than cow milk.
Data regarding the mineral contents of goat milk as compared with those of human and cow milk can be obtained from Table 1. The ash content of goat milk ranges from 0.7 to 0.85 percent. It will be noted that goat milk contains less sodium but more potassium and chlorine than cow milk. Reported concentrations of iron and copper in goat milk vary widely. The concentrations of other trace elements in goat milk are of the order of cow milk except for a lower cobalt and molydenum content.33
The vitamin contcnt of goat milk as compared to those of cow and human milk are also obtainable from Table 1. The vitamin content of goat milk is comparable to that of cow milk except for Vitarnin B6, folic acid and Vitamin B12 which are lower in goat milk. Compared to mothers' milk, goat milk contains the seine amount of folic acid and slightly less B12.
This was the designation given to a macrocytic — hyperchromic megaloblastic anemia which was observed in infants fed a diet of goat milk in Europe during the 1920s and 1930s.34, 35 Although the major difference between cow and goat milk in rcspoct to the content of vitwnins was observed to be Vitamin B12 and not folic acid, present day expcriencd indicates that infants with this macrocytic inegaloblastic ancmia respond more readily to therapy With folic acid than to Vitarnin B12. It was suggested by Gasser36 that goat milk anemia be described as a macrocytic hyperchromic megaloblastic infant anemia which responds to folic acid therapy.
Collins,35 in reviewing goat milk anemia came to the conclusion that the majot deficiency in infants with goat milk anemia is probably Colic acid. In view of the known inter-relationship between Vitamin B12 and folic acid, he suggests that the folic acid requirement be increased in infants fed the Vitamin B12 low goat milk diet.
In view of the above, it was suggested by several authors that goat milk be fortified with folic acid when used as an infant feed. Experimental work proved that by adding folic acid the nutritional value of goat milk was elevated to the same level as cow milk.
An interesting observation made by Glansmann37 and confirmed by Freudenberglll was that in all the typical anemias, the goat milk used was obtained from animals that were kept in pens and did not receive any green fodder or foliage whatsoever. Collins35 states that we presently know that green foliage is rich in folic acid and is of the opinion that this might have played a major part in the etiology of reported cases. Another important observation made by Von Klaus Betke and Gantert39 was that afl the reported cases had an infection, were malnourished and dystrophic. These two factors may have played a contributive part in the etiology. In reflection to the problem and after reading the paper of these two authors, we are wondering whether the above mentioned factors were not essential elements in the development of goat milk anemia during the two years, 1975 and 1976, evaporated goat milk was used in over 100,000 infants in South Africa. To our knowledge, not a single case of true goat milk anemia was reported. Could this be attributed to the fact that the goat milk came from a well-nourished herd and were given to infants lacking the above two elements? Since January 1977, folic acid is added to the South African products. Whether this was necessary can be debated.
Good practice in infant nutrition requires familiarity with current knowledgc of allergic reactions to foods.32 Among foods which are most likely to upset infants, cow milk ranks at the top.1 Evaporated milk is usually less upsetting than powdered milk and powdered milk less than ordinary doorstep milk.1
If cow milk is suspected as a cause of also be sensitive to soya or become sensitive even to the refined products now available on the market.1 Apart from this, there are many potentially deleterious effects referable to the soybean and it would seem preferable to attempt to maintain nutrition with the use of mammalian-derived milks wherever possible, using the vegetable milks only in those instances where mammalian milk is not tolerated.2
Since heat denaturation renders milk less allergcnic, a fortuitous combination such as evaporated goat milk would seem to be an ideal substitute food for infants allergic to milk.4
Goat milk has been found to be well tolerated by these infants, especially those with gastrointestinal or respiratory symptoms and even those who suffered shock from ingestion of cow milk.40 Infantile eczema only occasionally responds to goat mdk substitution, due to the fact the etiology of infantile eczema is a complex one and ad allergy to cow milk is seldom a major factor in the etiology.40
Compared to cow milk the lower curd tension of goat milk and the different chemical and physical composition of its fat, as already discussed, suggests greater digestability. Apart from milk allergy, goat milk is a valuable aid in the problematic infant intolerant to formula derived from milk.
An interesting observation which needs further investigation: goat milk has been used with great success in cases of post gastroentiritis as well as the initial stage of management of kwashiorkor where gastrointestinal hyper-sensitivity is experienced.
1. Van der Horst, R.L., S.Afr. med. J., 50, 927 (1976).
2. Fries, J.H., J.A.M.A., 165, 1542 (1957).
3. Jester, WR., Wright, W.W. and Welch, H., Antibiot. 9, 397 (1959).
4. Fries, J.H., Lightstone, A.C., Ann. of Allergy, 20, 351 (1962).
5. F.A.0. Production Yearbook, Vol. 20, Rome.
6. Sapperstein, S., Anderson, D.W., Journ. of Pediat., 61, 196 (1962).
7. Macy, I.G., Kelly, H.J. and Stoan, R.E., (1953, The Composition of Milks, Public. No. 254, Nat'l. Acad. of Sciences, Washington, D.C.
8. Kadiiski, E. (1952), Nauchi Trud Selskostop, Akad. Georgi Dimitrov 2, 23 (DSA 16:797).
9. Sirry, I. and Hassan, H.A. (1954), Indian J. Dairy Sci., 7, 188.
10. Nottbohm, F E. and Phillipi, K. (1933), X. Lebensmittelunters, U.-Forsch, 68,289.
11. Knowles, F. and Watkin, J.E. (1938) J. Dairy Res., 9.153.
12. Nirmalan, G. and Nair, M.K. (1962) Kerala Vet., 1, 49.
13. Canuti, A. and Saivadori, F. (1959) Latte 33, 25 (DSA 22:808).
14. Valen, A. and Valen, I.(1950), Meieriposten 39, 793.
15. Leonhard, I. (1963), Roczn, Naute roin. (Ser Zootechnika) 81, 535.
16. lzmen, E.R. (1940) Yuksek Ziraat Entitusu Calismalarindam iii (DSA 7:150)
17. Lythgoe, H. C. (1940), J. Dairy Sci. m 123, 1097.
18. Gamble, J.A., Ellis, N. R. and Bosley, A.K. (1939), Tech. Bull. U.S. Dept. Agric.
19. Webb, B. H. and Johnson, A. H. (1965) Fundamentals of Dairy Chemistry, Avi. Publi. Co., Westport, CT
20. Hofman, T., Nature, 181, 633.
21. Waugh, D., and Von Hippet, P H., J. Amer. Cham Soc. 78, 4576 (1956).
22. Melvin Lee, Rohitkumar, M and Lucia, S.P., Proc. Soc. Exp. Biol Med. (1962) 110 (1) 115.
23. Duman, B.R., Grosclaude, F. and Mercier, J.C. in Kretchmer, N., Rossi,E. and Sereni, F., eds (1 975): Modern Problems in Paediatrics, p. 46. Basle: S. Karger.
24. Gambie, J.A., Ellis, N. R. and Besfey, A.K, Tech. Bull. U.S. Dep. Agric., 671 (1939).
25. Daniels, A. L. and Sterns, G.: Am. J. Dis. Child. 30, 359.
26. Versell, A., Ztshr. lmmunitatsforch. 24:267,(1915).
27. Crawford, L.V. and Grogan, F.T., Journ. of Pediat., 59, 347 (1961).
28. Saperstein, S., Annals of Allergy, 18, 765 (1960).
29. Hanson, L.A. and Andersen, Acta Paediatrica 51, 509, (1962).
30. Fahmi, A.J., Sirry, I., and A. Safwat, Indian J. Dairy Sci., 9:124.
31. Jenness, R. and Parkash, S., Journal of Dairy Science 54, 1, 123-
32. Fomon, S., Infant Nutrition, p. 206 Philadelphia: N.B. Saunders.
34. Gyorgy, P.: Beitra zur pathogenese der ziegenmiichanamie, ztschr. Kilderh., 56:1.
35. Collins, R.A., Amer. J. of Clinical Nutrit. 11, 169 (1962)
36. Gasser, C., Helvet, Paediat. Acta, 3:301.
37. Glansman, E., Jb. Kinderhk. iii, 127 (1926).
38 Freudenberg, E., Ann. paediatri. 169, 103 (1927).
39 Betke, K and Gantert, L. Dtsch. med. Wschr, 176, 1342 (1951),
40 Hill, L.W., J. Pediat. 47 656 (1955).
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